<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      const user = {
        name: "jack",
        jump() {
          // let this;
          console.log("jump:", this);
        },
      };
      function say() {
        // let this;
        console.log("say:", this);
      }
      user.sayHello = say;
      user.add = function (x, y) {
        console.log("add:", this === user);
      };
      user.add();
      user.jump();
      user.sayHello();
    </script>
  </body>
</html>
